22 · Diagnostics

Engine knock

Make: Fiat
Model: Doblò Factory Service Manual
Year: 2000–2010
Section: Noisy / vibrations › Engine knock

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Fault diagnosisEngine knock

ENGINE KNOCK

The engine makes a cyclical noise, the intensity of which varies with the load and is noticeable during brisk acceleration and when long ratios are used

1	CHECK WITH DIAGNOSTIC EQUIPMENT	All OK	Problems met	Operation
		Results of the tests
	Connect the diagnostic equipment to the diagnostic socket and check: that there are no faults in the engine management control unit	Continue to Step 2	An error is detected in the control unit	Continue following the instructions for the diagnostic equipment
2	CHECKING AUXILLARY COMPONENTS	All OK	Problems met	Operation
	Disconnect the services belt and check whether the noise disappears. Do not let the engine run for long with the belt disconnected	Continue to Step 3	The noise disappears	See table S10 ENGINE WHILSTLING / SERVICES BELT NOISY
3	CHECKING LOCATION OF KNOCK	All OK	Problems met	Operation
	Carry out a test to locate the precise area from which the knocking is coming, using suitable equipment)	Continue to Step 4	The knocking is coming from the cylinder head	Continue to Step 5
		Continue to Step 4	The knocking is coming from the cylinder block/crankcase	Continue to Step 4
4	CRANKCASE KNOCKING CONDITION CHECK	All OK	Problems met	Operation
	Carry out a test to identify the conditions in which the knocking from the crankcase occurs.	Continue to Step 5	The knocking occurs with the engine cold, decreases with the engine hot and can be heard when releasing the accelerator.	Overhaul the engine, in particular check the condition of the pistons and replace them if necessary. Op. 1028H14
			The knocking occurs with the engine cold and increases during full acceleration with a long ratio.	Overhaul the engine: in particular, check the condition of the main bearings and replace them if necessary. Op. 1024A10
			The knocking is of a low intensity when cold but increases with the engine warm	Overhaul the engine: in particular, check the condition of the gudgeon pins and replace them. Op. 1028H60
			The knocking can be heard at all temperatures	Overhaul the engine: in particular, check the condition of the big end bearings and replace them if necessary Op. 1024A10
			The knocking can be heard at all temperatures and decreases when the clutch pedal is pushed.	Overhaul the engine and check the crankshaft end float. Op. 1024A10
	Carry out a test to identify the conditions in which the knocking from the crankcase occurs.	Continue to Step 5	The knocking occurs with the engine cold, decreases with the engine hot and can be heard when releasing the accelerator.	Overhaul the engine, in particular check the condition of the pistons and replace them if necessary. Op. 1028H14
			The knocking occurs with the engine cold and increases during full acceleration with a long ratio.	Overhaul the engine: in particular, check the condition of the main bearings and replace them if necessary. Op. 1024A10
			The knocking is of a low intensity when cold but increases with the engine warm	Overhaul the engine: in particular, check the condition of the gudgeon pins and replace them. Op. 1028H60
			The knocking can be heard at all temperatures	Overhaul the engine: in particular, check the condition of the big end bearings and replace them if necessary Op. 1024A10
			The knocking can be heard at all temperatures and decreases when the clutch pedal is pushed.	Overhaul the engine and check the crankshaft end float. Op. 1024A10
5	CHECK ON VALVE CLEARANCES	All OK	Problems met	Operation
	Check the valve tappet clearance Op. 1036H14	Continue to Step 6	Clearance not correct	Adjust the valve clearance Op. 1036H10
6	CHECKING CYLINDER HEAD	All OK	Problems met	Operation
1.2 8v	Overhaul the cylinder head and, in particular, check The operation of the hydraulic tappets That the cams are not worn Axial clearance to cams. Valves and corresponding clips.	Continue to Step 7	Cam worn or incorrect camshaft clearances	Restore or replace the components involved
1.9 DIESEL	Overhaul the cylinder head and, in particular, check Injectors The operation of the hydraulic tappets That the cams are not worn Axial clearance to cams. Valves and corresponding clips.	Continue to Step 7	Cam worn or incorrect camshaft clearances	Restore or replace the components involved
7	CHECK ON CORRECT OPERATION	All OK	Problems met	Operation
	Check that the fault is no longer present		Fault persists	Search for the fault starting from another symptom'

‹ Prev Airbag failure warning light off / (do not carry out initial test)Next › Engine hissing

Parts & tools for this job Staging For 2000 Fiat Doblò

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